Question

write relation between focal length and radius of curvature curvature​

Answer 1

Answer:

Focal length and radius of curvature are related as: f=2R.

Explanation:

Focal length (f) is the distance from mirror at which the light rays coming parallel from infinity meet.

Radius of Curvature R is the radius of the sphere of which the mirror is a part.

Focal length and radius of curvature are related as:

f=

2

R

Answer 2

Answer:

The relationship between the focal length f and radius of curvature ris r = 2f.

Explanation:

Consider a ray of light AB, parallel to the principal axis and incident on a spherical mirror at point B. The normal to the surface at point B is CB and CP = CBR, is the radius of curvature. The ray AB, = after reflection from mirror, will pass through F (concave mirror) or will appear to diverge from F (convex mirror) and obeys the law of reflection i.e.

i = r.

From the geometry of the figure,

ZBCP = 0 = i

In D CBF, 0 = r

::BF = FC (because i = r)

If the aperture of the mirror is small, B lies to P, and therefore BF = PF

Or FC = FP = PF

Or PC = PF + FC = PF + PF

Or R = 2 PF = 2f

Or f = R/2

Similar relation holds for convex mirror also. In deriving this relation, we have assumed that the aperture of the mirror is small.